Epidemiologische und laborexperimentelle Untersuchungen zur Urolithiasis bei Katzen

A long-term study (1981 – 2000) of the epidemic situation of
urolithiasis in cats in Europe is presented in the first part of
the work. Altogether 1.797 urinary stone analyses were established
with the help of infrared spectroscopy of cats. It was struvite
that was most often registered (64,2 %), followed by calcium
oxalate (26 %). Proteine stones (1 %) were proved only within our
investigation. The following breeds were mainly presented: European
Shorthair (i. e. domestic shorthair) on the basis of their share in
the whole population and Persian because of their predisposition to
urolithi-asis. Calcium oxalate incidence increased from 2,2 – 5 %
(1981 – 1990) to 33 % during the period of 1991 – 2000. Especially
Persian, Chartreux, British Blue, Birman, Exotic Shorthair,
Himalayan, Burmese, Somali und Ragdoll are susceptible to calcium
oxalate formation. The average age of all involved cats was about
6,85 concerning female cats and 6,47 concerning male cats, the
weight ─ about 5 kg for female cats and 5,4 kg ─ for male cats.
More than 50 % of pets (according to the information given by the
treating veterinary surgeons) were obese. During the investigation
55,1 % male and 44,9 % female cats were registered. The amount of
castrated cats made up 88,8 %. The average rate of relapse of all
kinds of urinary stones was about 27,6 %. The urinary calculi were
located mainly in the bladder and/or in the urethra. The surgical
ablation took place in 82,8 % of cases. 77,9 % of urinary stones
were accompanied by lower urinary tract inflammation. In 91 % of
cases it was the matter of infection. Most of the examined cats
were fed with dry- (30,1 %) or canned- and dry food. It is
importatant to underline that 42 % of all calcium oxalate stone
patients were given only dry food. The urinary stones appeared in
40 % either as pure urinary semolina or as the combination of
semolina and urinary stones. In the second part of this work 142
spontaneous urine samples of healthy cats were quantitatively
analysed and statistically evaluated. Thus the referential area for
the following urinary parameters of cats (relevant to calculus
formation) was made: calcium, oxalic acid, magnesium, citric acid,
phosphate, natrium, kalium, ammonium, sulphate, chlorine, uric
acid, creatinine, urea, specific gravity, urinary pH and
glyco-saminoglycan (GAG). And besides the relative supersaturation
with calcium oxalate (RSCaOx = 1,63) and struvite (RSStru = 0,451)
were assessed on the basis of urinary analyses with the help of
EQUIL 2. Synthetic urine was produced on the basis of the
established data (in the origi-nal research) of the composition of
native cat’s urine. It was used for the crystallization tests of
the formation of urinary stones in cats. The synthetic urine for
cats consisted of the following components: calcium, oxalic acid,
magnesium, citric acid, phosphate, natrium, kalium, ammonium,
sulphate, chlorine, uric acid, creatinine and urea. The artificial
urine did not possess any tendency to an independent change and was
well reproductive. It was checked with the help of the synthetic
cat’s urine in 3 test models the influence of the most important
for stone formation substances (calcium, oxalate und magnesium)
within their physiological arias in connection with urinary pH on
the urolith formation. The results were presented in diagrams. The
increase of the concentration of calcium in the carried out tests
resulted in no calcium oxalate crystallization. However, just a
small rise of oxalate (from [Ox] = 1,8 mmol/l) in acidic milieu
(from pH = 5,5) caused the formation of calcium oxalate. The rise
of magnesium concentration (over [Mg] = 3 mmol/l) prevented the
formation of calcium oxalate. On average the crystallization of
calcium oxalate in “oxalate-” and “magnesium model” began at RSCaOx
= 6,65 ± 0,44 (EQUIL 2). The maximum RSCaOx, the synthetic cat’s
urine could achieve without becoming solid, was 6,0 ± 0,32.
Regardless of the concentration of the substances that were
checked, struvite fell out at urinary pH 7,5 in all model series.
The increase of the concentration of calcium (from [Ca] = 0,9
mmol/l) and urinary pH resulted in the crystallization of different
phosphate phases (brushite and carbonate apatite). The results of
the epidemiological and experimental tests are the basic know-ledge
for the further work. With their help it is possible to test the
influence of different inhibitors and promoters on the
crystallization of calcium oxalate.